In communications networks, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed.
For example, various short-range radio technologies, such as Bluetooth and IEEE 802.15.4, operate in two phases: a discovery phase and a communications phase. In the discovery phase the devices of the communications network sense for other devices within their radio range. If a device is sensed and a connection to that device is desired, the connection is set up using additional signaling.
In more detail, in the discovery phase a device may send periodic broadcast radio beacons and/or listens for them by sensing a communications channel. When a beacon from another device is sensed, the information in the beacon can be used to initiate the connection between the two devices.
For example, in Bluetooth Low Energy (BLE), the discovery mode is defined as a combination of two states: an advertising state and a scanning state. In the advertising state the devices send advertisement packets and in the scanning state the devices listen to the advertising of other devices by sensing the channel. The scanning may be active or passive; in active scanning the device sends scanning request to a detected device. The detected device answers by sending a scanning response. In passive scanning the device just senses the channel for advertisement packets without transmitting anything.
For example, to enable communications between two devices in BLE one of these devices needs to be in the advertising state and the other of these devices needs to be in the initiating state (thus sensing the channel for advertisement packets and sending a connection request when sensing such an advertisement packet).
In general terms, the above outlined discovery phase consumes substantial amount of power in the devices since it requires devices to send beacons and/or to listen for beacons by sensing the channel for extended periods of time. In turn, this requires having the radio parts of the devices active. This may be an issue for battery-constrained devices.
Hence, there is still a need for an improved discovery in communications networks.